package demo1222.am;


import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Demo_03 {
    public static void main(String[] args) {
        List<String> s = new ArrayList<>();
        s.add("32456");

        Set<String> set = new HashSet<>();
        set.add("hello");
        boolean b = set.add("hello");
        System.out.println(b);

    }
}
